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Pollution of the Ocean by Sewage, Nutrients, and Chemicals

Coastal waters receive a variety of land-based water pollutants, ranging
from petroleum wastes to pesticides to excess sediments. Marine waters
also receive wastes directly from offshore activities, such as ocean-based
dumping (e.g., from ships and offshore oil and gas operations).

One pollutant in the ocean is sewage. Human sewage largely consists of
excrement from toilet-flushing; wastewater from bathing, laundry, and
dishwashing; and animal and vegetable matter from food preparation that is
disposed through an in-sink garbage disposal. Because coasts are densely
populated, the amount of sewage reaching seas and oceans is of particular
concern because some substances it contains can harm
ecosystems
and pose a significant public health threat. In addition to the nutrients
which can cause overenrichment of receiving waterbodies, sewage carries an
array of potentially disease-causing microbes known as pathogens.

Animal wastes from feedlots and other agricultural operations (e.g.,
manure-spreading on cropland) pose concerns similar to those of human
wastes by virtue of their microbial composition. Just as inland rivers,
lakes, and
groundwater
can be contaminated by pathogenic microbes, so can coastal waters. Runoff
from agricultural areas also contains nutrients such as phosphorus and
nitrogen, which can cause overenrichment in coastal regions that
ultimately receive the runoff.

The major types of ocean pollutants from industrial sources can be
generally categorized as petroleum, hazardous, thermal, and radioactive.
Petroleum products are oil and oil-derived chemicals used for fuel,
manufacturing, plastics-making, and many other purposes. Hazardous wastes
are chemicals that are toxic (poisonous at certain levels), reactive
(capable of producing explosive gases), corrosive (able to corrode steel),
or ignitable (flammable). Thermal wastes are heated wastewaters, typically
from power plants and factories, where water is used for cooling purposes.
Radioactive wastes contain chemical elements having an unstable nucleus
that will spontaneously decay with the concurrent emission of ionizing
radiation.

Sewage and Agricultural Wastes

Sewage originates primarily from domestic, commercial, and industrial
sources. In many developed countries, these wastes typically are
delivered either to on-site septic systems or to centralized sewage
treatment facilities. In both methods, sewage is treated before being
discharged, either underground (in the case of septic tanks) or to
receiving surface-water bodies (in the case of sewage treatment plants),
typically a stream, river, or coastal outlet.

Although sewage treatment facilities are designed to accommodate and
treat sewage from their service area, partly treated or even untreated
sewage sometimes is discharged. Causative factors include decayed
infrastructure
; facility malfunctions; or heavy rainfall events which overwhelm
systems using combined sewers and stormwater drains (known as combined
sewer overflows). In unsewered areas, improperly designed or
malfunctioning septic tanks can contaminate groundwater and surface
water, including coastal waters. In some developed regions (e.g.,
Halifax Harbor in Nova Scotia, Canada), raw sewage continues to pour
into harbors, bays, and coastal waters. In developing countries with no
on-site or centralized sanitation facilities, no opportunity exists for
any type of treatment, and human wastes go directly into surface waters,
including the coastal ocean.

Sewage Sludge.

Another source of ocean pollution by sewage-related waste is the
disposal of biosolids, a semisolid byproduct of the sewage treatment
process, often called sludge. Historically, sludge in developed nations
was disposed in coastal waters: New York's twenty sewage
treatment plants, for example, once disposed their sludge offshore in a
region known as the New York Bight. Although today's
environmental regulations in the United States prohibit this practice,
sewage sludge is still disposed at sea in some countries.

Disease-causing microbes are the primary human health risk in
sewage-contaminated waters, and the main cause of recreational beach
closures. Here a sign warns San Diego beachgoers of sewage in the
waters.

Agricultural Wastes.

Animal wastes often reach waterbodies via runoff across the land
surface, or by seepage through the surface soil layers. Hence,
agricultural runoff containing animal wastes does not receive any
"treatment" except what is naturally afforded by microbial
activity during its transit to a waterbody. In coastal watersheds, these
wastes can flow through river networks that eventually empty into the
sea.

Coastal Eutrophication.

Nutrients and organic materials from plants, animals, and humans that
enter coastal waters, either directly or indirectly, can stimulate a
biological, chemical, and physical progression known as eutrophication.
Coastal eutrophication is commonly observed in
estuaries
, bays, and marginal seas. In a broad sense, coastal eutrophication
mirrors the eutrophication of lakes. For example, as increased nutrients
stimulate algal and other plant growth, light transmission decreases.
The eventual bacterial decay of algae and other plants lowers the
dissolved oxygen level in the water. In extreme cases, all of the oxygen
can be removed.

Human-accelerated eutrophication (known as cultural eutrophication) can
be triggered by inputs of sewage, sludge, fertilizers, or other wastes
containing nutrients such as nitrogen and phosphorus. As recently as the
1980s, for example, the New York Bight was essentially lifeless due to
oxygen depletion, caused largely by decades of sewage and sludge
disposal. As of 2002, Halifax Harbor was still receiving a daily influx
of raw sewage, creating serious ecological and public health concerns.

Nutrient-enriched runoff from agricultural land in the midwestern United
States is the primary cause of the well-known Gulf of Mexico
"Dead Zone." Half of the U.S. farms are located in the
Mississippi River Basin, whose entire drainage basin empties into the
gulf. Much of the nitrogen reaching the gulf is from agricultural
fertilizers, with lesser amounts from residential fertilizers and other
sources. The water of the 20,000-kilometer (7,728-square-mile) Dead
Zone, extending from the mouth of the Mississippi River Basin to beyond
the Texas border, has so little oxygen that essentially no marine life
exists.

If human-accelerated eutrophication is not reversed, the entire coastal
ecosystem ultimately may be changed. Sensitive species may be replaced
by more tolerant and resilient species, and biologically diverse
communities may be replaced by less diverse ones. Further, nutrient
enrichment and the associated eutrophication in coastal waters is
implicated in some harmful algal blooms, in which certain species of
algae produce biotoxins (natural poisons) that can be transferred
through the food web, potentially harming higher-order consumers such as
marine mammals and humans.

Human Health.

Sewage, particularly if partially treated or untreated, brings high
microbe concentrations into the ocean. Human diseases can be caused by
waterborne pathogens that contact the skin or eyes; waterborne pathogens
that are accidentally ingested when water is swallowed; or foodborne
pathogens found in the tissues of fish and shellfish consumed as
seafood.
*

Beach pollution consequently is a persistent public health problem.
Annually, thousands of swimming advisories and beach closings are
experienced because high levels of disease-causing microbes are found in
the water. Sewage often is responsible for the harmful microbial levels.

Seafood contaminated by sewage-related pathogens sickens untold numbers
of people worldwide. Regulatory agencies will close a fishery when
contamination is detected. However, many countries lack regulatory
oversight or the resources to adequately monitor their fisheries.

Industrial Wastes

Industrial wastes primarily enter coastal waters from terrestrial
(land-based) activities. Industries, like municipalities and other
entities that generate wastes, dispose of many liquid wastes through
wastewater systems (and ultimately to waterbodies), whereas they dispose
of their solid wastes in landfills.

The quantity and characteristics of industrial wastewater depends on the
type of industry, its water and wastewater management, and its type of
waste pretreatment (if any) before delivery to a wastewater (sewage)
treatment plant. Because industrial waste frequently goes down the same
sewers as domestic and commercial nonindustrial waste, sewage often
contains high levels of industrial chemicals and heavy metals (e.g.,
lead, mercury, cadmium, and arsenic).

Substances that are not removed by wastewater treatment processes are
discharged via the treated effluent to a receiving stream, river, or
coastal outlet. Inland waters ultimately reach the ocean, carrying with
them some residual chemical that are not attenuated, stored, or degraded
during their journey through the watershed. Other land-based sources of
industrial pollutants in the ocean are pipeline discharges and
transportation accidents, leaking underground storage tanks, and
activities at ports and harbors. Intentional, illegal dumping in inland
watersheds and in inland waterbodies also can deliver industrial wastes
to drainageways, and ultimately to the ocean.

In coastal watersheds, some industries discharge their wastes directly
to the ocean. Like industries located inland, these industries must
first obtain a permit under the Clean Water Act. Industrial pollutants
also can directly enter the ocean by accidental spills or intentional
dumping at sea.

Wet and dry deposition of airborne pollutants is a sometimes overlooked,
yet significant, source of chemical pollution of the oceans. For
example,
sulfur dioxide from a factory smokestack begins as air pollution. The
polluted air mixes with atmospheric moisture to produce airborne
sulfuric acid that falls on water and land as acid rain. This deposition
can change the chemistry and ecology of an aquatic ecosystem. The major
transport of PCBs to the ocean, for example, occurs through airborne
deposition.

Industrial chemicals can adversely affect the growth, reproduction, and
development of many marine animals. Pollutants are appearing not only in
the Pacific, Atlantic, and Indian Oceans and their marginal seas, but
also in the more remote and once-pristine polar oceans. An array of
contaminants have been found in the flesh of fish and marine mammals in
polar regions. In addition to the environmental and ecological issues,
there is growing concern over the potential human health impacts in
aboriginal communities whose residents depend on fish and marine mammals
for daily sustenance.

A major public health concern is the safety of seafood as it relates to
the chemical pollution of waters used for commercial and recreational
fishing and
mariculture
. Heavy metals (e.g., copper, lead, mercury, and arsenic) can reach high
levels inside marine animals, and then be passed along as seafood for
humans. A well-known case of human poisoning occurred in Japan, where
one industry dumped mercury compounds into Minimata Bay from 1932 to
1968. Methyl mercury that accumulated in fish and other animals was
passed along to humans who consumed them. Over 3,000 human victims and
an unknown number of animals succumbed to what became known as
"Minimata Disease", a devastating illness that affects the
central nervous system.

Monitoring by fisheries, environmental, and public health agencies can
prevent or minimize cases of human illness caused by chemical
contaminants in seafood. Some shellfish-producing areas off the U.S.
coasts have been either permanently closed or declared indefinitely
off-limits by health officials as a result of this type of pollution. A
large percentage of U.S. fish and shellfish consumption advisories are
due to abnormally high concentrations of chemical contaminants in
seafood.

Regulatory Controls

The 1890 River and Harbors Act prohibited any obstruction to the
navigation of U.S. Waters, and hence regulated the discharge of dredged
material into inland and coastal waters. By weight, dredged material
comprises 95 percent of all ocean disposal on a global basis. Its
regulation (administered by the U.S. Army Corps of Engineers)
increasingly is being accomplished in concert with broader concerns,
including ecological integrity and other public interests.

In 1972, the U.S. Congress passed the Marine Protection, Research, and
Sanctuaries Act (Ocean Dumping Act) and the Federal Water Pollution
Control Act Amendments (Clean Water Act) that, among other goals,
prohibited the disposal of waste materials into the ocean, and regulated
the discharge of wastes through pipelines into the ocean. The Ocean
Dumping Act requires the federal review of all proposed operations
involving the transportation of waste materials for the purpose of ocean
dumping, and calls for an assessment of the potential environmental and
human health impacts. The U.S. Army Corps of Engineers and U.S.
Environmental Protection Agency implement the permit programs associated
with these laws.

In the United States, ocean dumping of industrial wastes is
prohibited. Yet the vastness of the open sea provides a haven for
illegal dumping.

The Ocean Dumping Ban Act of 1988 significantly amended portions of the
1972 Ocean Dumping Act, and banned ocean dumping of municipal sewage
sludge and industrial wastes (with limited exceptions) by phased target
dates. The disposal of sewage sludge in waters off New York City was a
major motivation for its enactment. Ocean disposal of sewage sludge and
industrial waste was totally banned after 1991. Narrow exceptions were
created for certain U.S. Army Corps of Engineers dredge materials that
occasionally are deposited offshore. Dredging is necessary to maintain
navigation routes for trade and national defense. Consequently,
allowable ocean dumping in the United States since 1991 has essentially
been limited to dredge material and fish wastes.

Two international conferences in 1972—the UN Conference on the
Human Environment, and the Intergovernmental Conference on the
Convention on the Dumping of Wastes at Sea—were the result of
international recognition of the need to regulate ocean disposal from
land-based sources on a global basis. These conferences resulted in an
international treaty, the Convention on the Prevention of Marine
Pollution by Dumping of Wastes and Other Matter (also known as the
London Convention).

Another treaty addressing the issue of wastes disposed from vessels was
adopted in 1973. The International Convention for the Prevention of
Pollution from Ships (or MARPOL) calls for signatory nations to enforce
bans on dumping oil and noxious liquids into the ocean from ships, but
the disposal of hazardous substances, sewage, and plastics remains
optional.

As per the U.S. regulations, the dumping of industrial wastes,
radioactive wastes, warfare agents (chemical or biological), sewage, and
incineration at sea are directly prohibited. Moreover, the ocean
disposal of other waste materials containing greater than trace amounts
of certain chemicals is strictly prohibited. Allowed under strictly
regulated conditions are the ocean disposal of relatively uncontaminated
dredged material (harbor sediments), geologic material, and some fish
waste; burial at sea; and ship disposal.

In 2000, the U.S. Congress enacted the Beaches Environmental Assessment
and Coastal Health Act (BEACH Act) to reduce the risk of disease to
users of the nation's coastal and Great Lakes waters. Funds are
being made available for states and tribes to establish monitoring
programs for disease-causing microbes, and to notify the public when
monitoring indicates and public health hazard.

SEWAGE FROM VESSELS

The Clean Water Act regulates the discharge of sewage from commercial
and recreational vessels. The U.S. Environmental Protection Agency,
Coast Guard, and individual states work jointly to protect human health
and the aquatic environment from disease-causing microorganisms which
may be present in sewage from boats. The act established standards for
marine sanitation devices and nodischarge zone designations for vessels.
As of 2002, seventeen coastal and Great Lakes states had designated part
or all of their surface waters as no-discharge zones. Also that year,
the Environmental Protection Agency and Coast Guard were assessing
potential regulatory amendments that would more stringently regulate
discharges from cruise ships in offshore waters.

*
See "Human Health and Water" for a summary of common
waterborne pathogens.

User Contributions:

i am doing a project on this and im completley shocked.
How can these people carry on dumping chemicals into the water.
Its cruel and its killing wildlife.
I hope it stops.
I am furious, know one understands how much damage this is causing.
We need to stop.
We should all come togther to stop this!!!
Email me back

Due to the 'Halifax Harbour Solutions', a reported $333 million dollar project, raw sewage is no longer dumped into the Halifax Harbour. The treatment plan was in operation in 2008, however a massive failure in one of the three plants happened in Jan. of 2009. The plant was repaired and online in the spring of 2010. The water was cleared for public swimming in July of 2010.

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